Impulse transmitter



Oct. 12, 1948. R. SARGISSON ETAL 2,451,358

IMPULSE TRANSMITTER Filed Aug. 24, 1944 :5 Sheets-Sheet 1 N D Ll.

N 0 N r- Q w Ll. LO I I a? Q INVENTOR 7 HERBERTF. OBERGFELL, DE SED 0 BY AMANDA OBERGFELL,E)(ECUTR|X g N BY ROBERT L. SARGISSON ATTORNEY 1948' R. L. SARGISSON ETAL 2,451,358

IMPULSE TRANSMITTER Filed Aug. 24, 1944 I 3 Sheets-Sheet 2 F IG.4 H65 WEDED 54 2| S INVENTORS.

HERBERT F. OBERGFELL, DECEASED BY AMANDA OBERGFELL, EXEGUTRIX ROBERT L. SARGISSON ATTORNEY 1948. R. L. SARGISSON ETAL 2,451,353

IMPULSE TRANSMITTER J Filed Aug. 24, 1944 3 Sheets-Sheet 3 FIG.I6

IN V EN TORS BY AMANDA OBERGFELL,EXECUTRIX ROBERT L. SARGISSON ATTORNEY HERBERT OBERGFELL, DECEASED Patented Got. 12, 1948 UNITED STATES PATENT OFFICE IMPULSE TRANSMITTER Robert L. Sargisson, Berwyn, 111., and Herbert F. (libergfell, deceased, late of River Forest, 111., by Amanda Ghergfell, executrix, River Forest, 111., assignors to Automatic Electric Laboratories, lino, Chicago, Ill., a corporation of Belaware Application August 24, 1944, Serial No. 551,010

23 Claims. 1

The present invention relates in general to automatic telephone systems and more particularly to an improved impulse transmitting arrangement for controlling automatic switches.

main object of the present invention is the provis on of an improved push-button, or key actuated, calling device mounted in an ordidesk telephone in place of the usually welllrnown rotary calling device.

One of the features of the invention relates to the improved construction of such a calling device which permits speedy and accurate setting up or" the called digits in a telephone number whereby the digit keys may be actuated as fast as a p rson can normally actuate the successive dig b keys corresponding to a telephone without waiting an appreciable time between each actuation.

Another feature relates to the means whereby the cal device is arranged to transmit a ground pd se, loop pulses, or a combination of loop and ground pulses dependent upon the key actuated.

Gther features of the invention relate mainly to the construction and arrangements of the operating mechanism of the calling device and will. be apparent from the following de scription and in the claims.

The pushbutton calling device along with a mechanical dial repeater and intervening circuits was designed primarily for use by a person who originates a large number of outgoing calls, such as a salesman, an order clerk, or a private branch exchange operator who completes outgoing trunk calls from a local private branch exchange to automatic subscribers lines accessible through automatic switches in the main exchange.

The calling device is arranged to transmit a of five pulses comprising only loop pulses or a combination of loop and ground pulses the i tervening circuits. For example, the transmic on of the digit comprises five loop pulses and the transmission of the digit 9 comprises four loop pulses followed by a ground pulse. These loop pulses being in effect two separate operating pulses, one pulse each over each or" the two line conductors, while the ground pulse is only one operating pulse transmitted over only one of the two line conductors,

thereby effecting a total of operating pulses which equals the value of the digit being transmitted. In this manner, the transmitted digit T. comprises a single ground pulse, the digit 2 comprises a single loop pulse, the digit 3 comprises a loop and a ground pulse, etc. Therefore, the number of loop impulses transmitted for the digits equals one-half the value of the digits followed by a ground pulse for the last pulse in the case of the odd digits. Since the calling device transmits a maximum of only five pulses, it is, therefore, capable of transmitting these pulses as fast as a person can mor m'ally operate the successive digit keys corresponding to a telephone number.

'Ewo line relays in the intervening circut operate in response to each loop pulse and only one of these relays operates in response to the ground pulse for controlling the operation of the mechanical dial repeater. This mechanical dial repeater takes two steps for each loop pulse and only one step for a ground pulse to register the incoming digits transmitted thereto. When the automatic switches are in condition to receive impulses, the mechanical repeater is automatically operated to transmit standard loop pulses in accordance with the digits registered in the mechanical dial repeater. The automatic switches are operated in response to these digits to complete the desired connection.

Referring now to the drawings:

Figure 1 shows a front or top View, partly in section 1 of the calling device;

Figure 2 shows a side view partly in section and witli certain parts removed in order to more clearly see and understand the operating functions of the calling device;

Figure 3 shows a rear view of the calling device;

Figures l, 5 and 6 show, respectively, a top, a side and an end view of the base plate or mounting plate of the calling device;

Figures 7 and 8 show a plan View and a side View of the rocker arm assembly for controlling the operation of the grounding contact springs;

Figures 9 and it show a plan view and a side View, while Figure 11 shows a partial cross section of the stirrup assembly for operating the geared segment;

Figures 12 and 13 show details of certain key levers and the rocker arm of the calling device in operated positions;

Figures 14 and 15 show a side and an end view of the clutch assembly of the calling device;

And Figure 16 shows the calling device mounted on a standard desk telephone.

Referring now to the drawings showing the calling device, the base 2i, or mounting plate, shown in detail in Figures 4, and 6, has a number of turned arms or extensions for mounting the various operating parts and a plurality of screw holes 22 for mounting the calling device to the desk telephone. The up-turned arms 23 are provided for mounting the shaft 24 on which the segment 25, key levers l to 0, inclusive, and the stirrup assembly shown in Figure 9 are rotatably mounted. The up-turned arms 26 are provided for mounting the rocker arm assembly 2?, shown in Figure 7. A stop 28 is provided for the rocker arm. The down-turned arms 29 are provided for mounting the impulse shaft 35]. The down-turned arm 35 is provided for mounting the housing end of the governor 32 and for mounting the plate 33 having an arm to which one end of the segment spring 3.; is secured. An L-shaped bracket 35 is secured to the base 25 by any suitable means such as welding or by means of screws for mounting the other end of the governor 32. A U-shaped bracket 36 is welded or otherwise secured to the base plate for mounting the shaft having the pinion and worm gears 32 and 33 for driving the governor 32. An L-shaped bracket 39 is secured to the base plate 2: by means of screws for mounting the grounding and shunt contact spring assemblies and a V-shaped bracket to is also secured to the base plate for mounting the impulsing contact springs.

A slot i! is provided in the base plate through which the segment 25 extends for operatin the clutch assembly. A rectangular hole 52 is also provided in base plate 2! through which the extension arm i? on the rocker arm assembly extends. A threaded hole 43 is provided for mounting the lock stud 455 and bracket 45. Threaded holes 45 are provided in the base plate by means of which the studs i5 and screws 126 secure the face plate IE to the base plate 2!.

The face plate l2, as best shown in Figure 1, is of an over-all circular shape and is provided with slots through which the key levers extend and which act also as guides for such levers. Additional guides M are welded to the face plate E2 to assist in guiding the key levers. A box it mounted on the face plate 52 covers the individual restoring springs l6 of the key levers.

Each of the key levers i to It, inclusive, are in general L shaped and each has a button with its corresponding digit on its outer arm which extends through the face plate. Each digit button may have a corresponding letter as well as a digit. Each of the other arms of the key levers is rotatably mounted on the shaft 24 and separated by spacers, or washers, ll. Each key lever has an extension, such as 513 and SE, to which the individual restoring springs it are fastened. The restoring springs it are each fastened to holes in the common bracket 56 which in turn is secured to the face plate I2. Each key lever has a hump such as 2A, 5A and 6A which acts as a stop to limit the return movement of the key when such humps strike the face plate l2. Each leverkey has a downward extension, or projection, such as 20, 5C and 60 which strikes the base plate 2| when the keys are actuated to variably limit the operating stroke of each key lever in accordance with the value of the actuated key. As will be noted the extension 2C, shown in Figure 2 is considerably longer than the extensions 50 and shown in Figures 12 and 13 and, therefore, the key lever 2 is only operated a short distance. These extensions vary in length so that the travel distance of the key levers vary, the lower numbered keys having a shorter stroke than the higher numbered keys. Key levers i and 2 have the shortest operating stroke, key levers 3 and 4 the next shortest operating stroke, key levers 5 and 6 have a longer operating stroke than key levers 3 and i, keylevers l and 8 have the next longer stroke, and key levers 9 and I0 have the longest stroke. Each extension has a cut-out portion such as 2D, 5D and 6D for controlling the operation of the rocker arm 41 and insulating member 48 (Figure 7). Each odd numbered key lever has a cut-out portion with sloping sides, such as shown at 5D, to engage the rocker arm bar or rod 56 and move the rocker arm 4? to the position shown in Figure 12. Each even numbered key lever has a cut-out portion with sloping sides, such as shown at 6D, to engage the rocker arm rod 50 and move the rocker arm 47 to the position shown in Figure 13 for the purpose of separating the grounding contact sprin i9.

With the above arrangement it will be noted that the key levers are divided into pairs, each pair having the same operating stroke, but each even numbered key lever of each pair due to its shaped cut-out portion, such as SD, operates the rocker arm assembly and insulating member 48 between the grounding contact springs 19 to disconnect ground from the substation circuit.

Each key lever, except the levers 9 and ill, has an arm or lever, such as arms 2E, 5E and 6E, loosely pivoted on such levers. These arms engage and slide along the base plate l2. When the keys are actuated until such time as the extensions such as 2C, 50 and 5C, strike the base plate !2 at which time these arms stop the stirrup bar or rod 52 to limit the movement of the segment 25 in accordance with the actuated key. Since the segment 25 must move variable distances for the diiferent actuated keys the arms, such as 2E, limit the movement of segment 25 in accordance with the key actuated and also act as stops to prevent the overthrow of the segment beyond the predetermined distance required of the segment for the particular actuated key.

A shaft 2% is fastened in the holes in the arms 23 by means of end screws i8 and on this shaft 2 the key levers I to it, inclusive, the segment 25, and stirrup assembly, better shown in Figure 9, are rotatably mounted. Spacers I? are provided between the various key levers, segment 25 and end stirrup bars 5!. The stirrup assembly shown in Figure 9 comprises end stirrup bars 5! having holes in their upper ends for rotation on shaft 24 and at their other ends are welded or brazed to the stirrup rod 52. The rod 52 extends across and below all of the key levers so that the operation of an one of the key levers actuates the'stirrup rod 52 a predetermined distance corresponding to the actuated key. The arms, such as 5E and 6E, on each of the key levers, as previously described, cooperate with the stirrup rod 52 to limit the operation of segment 25 a predetermined distance in accordance with the value of the actuated key thereby preventing overthrow of the segment beyond this predetermined dis tance.

The segment 25 has a slot 25A in which the stirrup rod 52 snugly fits so that any movement imparted to rod 52 by any key actuation also moves the segment 25. Segment 25 is rotatably mounted on shaft 24 and is normally held in its normal position with the edge portion 25B abutting against base plate 2! by the segment spring 34 which has one end looped through the hole 256 and the other end fastened to the arm 33. The teeth 25D on segment 25 mesh with the teeth on the clutch assembly shown in Figure 14.

The rocker arm assembly shown in Figures '7 and 8 comprise two end. bars 53 and 5 having holes at their upper ends by means or which the rocker arm assembly is loosel pivoted by rivets to the rip-turned arms 26 in base plate 2!. The rocker rod 50 is welded, or brazed, to the bars 53 and 54 and the rocker arm 41 is welded, or brazed, to the rod 56 as shown. An insulating plate 48 is riveted to the rocker arm 4'! for the purpose of separating the grounding contact springs Ell as previously described.

The clutch assembly shown in Figures 14 and is mounted on the main impulse shaft 38 so as to be freely rotated. thereon. This assembly comprises a pawl mounting segment 60 having teeth for meshing with the segment and two arms 6i and 62. The pawl 63 is pivotally mounted on the upright arm 6! and held in engagement with ratchet wheel 61 by means of pawl spring 54 which is fastened at one end to the ear on pawl 63 and at the other end to a pin $55 on the other arm 62 on the pawl segment 68. A sloping, or rounded, surface 56 on arm 62 is provided for operating the shunt contact springs H for the purpose of shunting the transmitter and receiver in the substation circuit when the clutch assembly is in an off -normal position. Integral with the pawl segment are two circular collars 6S and 12 in the latter of which a hole is drilled for inserting an insulatin pin 11 which is provided for operating and closing contact springs 73 during only the last impulse of each digit. A cam 65 staked to collar Ti is provided for controlling the operation of the impulse wheel locking bar T4.

The locking bar 14 is pivotally mounted on the stud collar 44 which is secured to the base plate 2| by means of machine screw 15. A spring 16 around the stud collar 44 has one end secured to the L-shaped bracket and the other end secured to the locking bar 14 for maintaining the bar 14 in between the teeth of the impulse wheel. The locking bar 14 locks the impulse shaft 3!] until such time as the clutch assembly is rotated by segment 25 whereupon the inclined surface of cam 68 raises the locking bar '14 out from between the teeth of the impulse wheel and onto the outer periphery of cam 68 to permit rotation of the impulse shaft.

The pawl 63 slides over the teeth of ratchet wheel 6! on the forward rotation of the clutch as-- sembly and on the return rotation of the clutch assembly the pawl 63 engages one of the teeth of the ratchet wheel 67 to rotate the ratchet wheel 61, shaft 30, governor gear 19, and impulse wheel 18, The main impulse shaft 30 together with the governor gear 19, ratchet wheel El and impulse wheel 18 now rotate in unison with the return movement of the clutch assembly. The governor gear 19, ratchet wheel 61 and impu se wheel 18 are secured to shaft 30 to rotate therewith while the clutch assembly is rotatably mounted on shaft 30 and only rotates in unison with the shaft 3Q on the return movement of the clutch assembly.

The governor gear T9 meshes with the governor pinion gear 3'! to drive the governor worm gear 38 which in turn drives the governor to determine the speed of rotation of impulse shaft 30. The teeth on impulse wheel 18 operate the impulsing contact spring 89 to transmit outgoing pulses. As cam 68 of the clutch assembly returns to normal, locking bar i l slides off of the periphery of the cam 68 after the last impulse and down the inclined surface in between two teeth of the impulse wheel TS to prevent any overthrow of the impulse wheel, the end of bracket 15 taking up any shock imparted to bar 74.

A circular collar dd between the base plate 2i and face plate i2 is provided for enclosing the operating mechanism located above the base plate 2!.

Havin given a description of the detail construction of the various parts of the calling device, a brief description will now be given of the operations which take place in response to the operation and release of one of the push-buttons. For example, it will be assumed that the number 5 push button is actuated and released by the user. In response to the downward pushing of number 5 push button, the key lever 5 is rotated on shaft 24 until the extension engages the base plate 2!, thereby limiting any further dowriward movement of key lever 5. During the downward rotation of key lever 5 the lower edge of this lever engages the stirrup rod 52 and thereby rotates the stirrup assembly and segment 25 only a predetermined distance because the arm 5E pivotally mounted on key lever 5 slides along the base plate 2i and its upper edge engages the stirrup rod 52 at the time extension 50 en ages base plate 2i to limit any further movement of segment 25 and rod 52. During the downward movement of key lever 5 and slot 5D engages rod 50 of the rocker arm assembly to move the rocker arm il and plate 52 to the position shown in Figure 12, thereby permitting the closure of grounding contact springs iii.

Also during the downward stroke of key lever 5 and the rotation of segment 25, the clutch assembly, comprising the pawl segment SE and its arms 5i and 82, the pawl 33, collars 69 and E2, insulating pin Ti and cam 68, is rotated by segment .25, a'distance corresponding to the predetermined distance of rotation of segment 25. The pawl 63 slides over a certain number of ratchet teeth, three in this case, since the segment was operated only a corresponding predetermined distance. The arm moves to permit closure of the shunt contact springs H the pin '5'! rotates to open contact springs 13 and the cam 63 moves locking bar M to unlock the impulse wheel l8 and shaft 30. All these operations are preparatory to the transmission of impulses.

After the user has actuated push-button 5, the key lever 5 is released and such lever restores to normal under control of its individual spring, such as spring 56. Segment spring 36. is now effective to restore segment 25 and the stirrup assembly to their normal positions. During the restoring movement of segment 25, the clutch assembly, due to the teeth in pawl segment Bil meshing with the teeth of segment 25, is also returned to normal. During the restoring movement of the clutch assembly the pawl 63 engages a tooth in ratchet wheel 61 with the result that the main impulse shaft 30, including the governor gear ES, ratchet wheel 6? and impulse wheel rotate in unison with the clutch assembly. In this manner the impulse shaft is only rotated on the return movement of the clutch assembly.

The governor gear is operates the pinion gear 3? and worm gear to operate the governor 32 to govern the speed of rotation of the impulse shaft 36.

The teeth in the periphery of the impulse wheel it actuate impulse contact spring 80 to engage contact spring 8i and open contacts 82 to trans mit impulses. Just prior to the operation of contact spring 86 for the last impulse, the insulating pin ll operates and closes contact springs 73 in order to transmit a ground impulse instead of a loop impulse for the last impulse in case contact springs l'il are closed by the operation of rocker arm d! and insulating plate @3 as shown in Figure 12. When the clutch assembly reaches normal, the bushing on shunt contact springs ll is operated by the sloping surface 66 on arm 62 to open the shunt contact springs ll to remove the shunt circuit from around the substation transmitter and receiver. The lock bar 74 slides off the periphery of cam 68 in between two teeth on the impulse wheel 73 when the clutch assembly reaches its normal position to prevent overthrow or any further operation of the impulse wheel.

During this operation two loop pulses and a ground impulse have been transmitted in response to the actuation and release of push button 5. in this case the last impulse was a ground. pulse instead of a loop impulse because the grounding contact springs it; were closed during such transmission period. In case the user now actuate-s the number push button, the key lever S is actuated to cause the same operations as described above with the exception that in this case the rocker arm 4? and insulating plate lli are operated by the slot BD on key lever 5 to separate grounding contact springs 79 so that the last impulse transmitted is a loop pulse instead of a ground impulse.

In a manner apparent from the foregoing the followin shows the number and character of the imp ise. transmitted for each digit:

Digit 1one ground impulse Digit 2-one loop impulse Digit 3one loop and one ground impulse Digit l-two loop impulses Digit 5--two loop impulses and one ground im- The subject matter of the present invention comprising the mechanical construction and operating functions of the push-button calling device is being claimed in the instant application. The subject matter relating to the mechanical dial r peater is being claimed in a copending application of Herbert F. Obergfell and Oscar W. Henrikson S. N. 554,912 filed September 20, 1944, U. S. Patent No. 2,445,829 dated July 27, 1948, while the subject matter relating to the circuits for cooperating with both the push-button calling device and the mechanical dial repeater is being claimed in a copendin application of Herbert F. Obergfell and John H. Voss S. N. 559,878 filed October 23, 1944, now U. S. Patent No. 2,418,609 dated April 8, 1947.

Having described the invention, what is considered new and is to have protected by Letters Patent will be set forth in the following claims.

What is claimed is:

i. In an impulse transmitter, a plurality of push keys corresponding to different digits, a shaft, a segment operated in response to the operation of any of said keys, a clutch assembly loosely mounted on said shaft, teeth on said segment meshing with teeth on said clutch assembly for moving said segment and clutch'assembly in unison, a spring for returning said segment and said clutch assembly, means for operatin said shaft only in response to the return movement of said segment and clutch assembly, an impulse wheel on said shaft operable therewith, and impulse contacts controlled by said impulse wheel for transmitting impulses.

2. In a transmitter a plurality of keys corresponding to different digits, a segmentoperated in a forward direction in response to the operation of any one of said keys, a spring for returning said segment in a return movement in response to the release of the operated key, a shaft, means for operating said shaft only in response to the return movement of said segment, an impulse wheel on said shaft and operable therewith, and impulse contacts controlled by said impulse wheel for transmitting a train of impulses corresponding to the key actuated.

3. In an impulse transmitter comprising a plurality of push keys corresponding to different digits, a main shaft, 2. segment operated in response to the operation of any of said keys, means for returning said segment to normal, a clutch assembly rotatably mounted on said shaft and rotated in unison with said segment, a ratchet wheel secured to said shaft, a pawl on said clutch assembly cooperating with said ratchet wheel for rotating said shaft in response to the return movement of said segment, an impulse wheel secured to said shaft, a locking lever cooperating with said impulse Wheel for locking said shaft and for preventing overthrow of said impulse wheel, a cam on said clutch assembly for controlling said locking lever to permit rotation of said shaft and impulse wheel, impulsing contacts controlled by said impulse wheel to transmit one or a train of impulses, shunt contacts, an arm on said clutch assembly for operating said shunt contacts, contact springs, and a pin on said clutch assembly for operating said contact springs on only the last transmitted impulse.

l. In an impulse transmitter comprising a plurality of push keys corresponding to different digits, a main shaft, a segment having a normal position and operated in response to the operation of any of said keys, means for returning said segment to normal position, a clutch assembly having a normal position and rotatably mounted on said shaft in unison with said segment, a ratchet wheel secured to said shaft, a pawl on said clutch assembly cooperating with said ratchet wheel for rotating said shaft in response to the return to normal of said segment, an impulse wheel secured to said shaft, impulsing contacts operated by said impulse wheel for transmitting one or a train of impulses, shunt contacts, an arm on said clutch assembly for operating said shunt contacts during the time said clutch assembly is off normal, contact springs, and a pin on said clutch assembiy for operating said contact springs on only the last impulse transmitted by said impulsing contacts.

5. In an impulse transmitter comprising a plurality of push keys corresponding to the different digits, an impulse shaft, a clutch assembly having a normal position and rotatably mounted on said shaft, means for rotating said clutch assembly from normal position in response to the actuation of any one of said keys, means for restoring said clutch assembly to normal position in response to the release of the actuated key, means for rotating said shaft only response to the restoring movement of said clutch assembly, an impulse wheel on said shaft and rotatable therewith, a locking lever cooperating with said impulse wheel for lockng said shaft and for preventing overthrow of said impulse Wheel, and a cam on said clutch assembly for controlling said locking lever to permit rotation of shaft and impulse Wheel during the time said clutch assembly is in an off-normal position.

6. In an impulse transmitter, a plurality of push keys corresponding to different digits, common stop plate, a projection on each of said keys for cooperation with said stop plate to limit the manual movement 01" each key in accordance with the value or" the corresponding digit, a segment operable in a forward movement in re sponse to the manual operation of any one of said keys, extent of forward movement of said segment being dependent upon the digit value of the k y actuated, means for returning said segment in a return movement in response to the release of the operated key, a shaft, means for operating said shaft in only one direction whereby said shat is operated only in response to the return movement of said segment, an impulse Wheel on said shaft and operable therewith, and impulse contacts controlled by said impulse wheel for transmitting a d comprising a train of impulses corresponding to the actuated key.

In an impulse transmitter, a plurality of push key levers corresponding to the different digits, means including different length projections on said key levers for limiting the manual movement of said key levers variable predetermined distances in accordance with the value of the corresponding digit, a common operate bar below said key levers free to move different distances in response to the manual operation of any one or" said key leve s, and means independent of said proje tions and including a lever on each of said key levers for limiting the movement of said common operate bar to different predetermined distances dependent upon the actuated key lever and for preventing overthrow of said common operate oar beyond said predetermined distances.

8. In an impulse transmitter, a first plurality of push keys corresponding to certain numerical digits, a second plurality of push keys corresponding to different numerical digits, a rocker arm common to all said keys, said rocker arm having a. first and a second position, means ior operating said rocker arm to its first position in response to the operation of any key in said first plurality, mean for operatin said rocker arm to its second posi n response to the o eration ol any key second plurality, and circuit co trolling contacts controlled by said rocker arm in its first and second positions.

9. In an impulse transmitter, a plurality of keys corresponding to the difierent digits, -plate common to said keys, projections on of said keys r cooperating with said stopplate to limit the manual movement of each key predetermined distance in accordance with the 1e corresponding digit, means responactua'tion and release of any one oi lfo transmitting a digit comprising one of 'ipulses corresponding to the actukeys or a

ated key, a rocker arm having a first and a second position, cut-out portions in each of said projections shaped to move said rocker arm to its first position or its second position in response to the operation of said keys dependent upon the value of the corresponding digit, and a pair of circuit controlling contacts closed by said rocker arm its first position and opened by said rocker arm in its second position.

it). In an impulse transmitter, a plurality of push keys corresponding to different digits, means responsive to the actuation and release of any one of said keys for transmitting a digit comprising one or a train of impulses corresponding to the actuated key, a rocker arm having a first and a second position and normally at st in either of said positions, projections on each of said keys having means therein for maintaining said rocker arm in its first position in response to the operation of any one of a portion of said plurality of said keys or for operating said rocker arm from said first position to said second position in case any one of the remaining portion of said plurality of said keys is actuated, and a pair of circuit controlling contacts closed by said rocker arm in its first position and opened by rocker arm in its second position.

ii. In an impulse transmitter, a plurality of push keys corresponding to diiierent digits, means responsive to the actuation and release of any one of said keys for transmitting a digit comprising a train of impulses corresponding to the actuated key, a rocker arm, said rocker arm having a first and a second position, means for operating said rocker arm to its first position in response to the operation of any one of certain of said means for operating said rocker arm to its second position in response to the operation of any one of the remaining keys of said plurality, circuit controlling contacts controlled by said rocker arm in its first and second positions, and other contacts operated only during the last transmitted impulse of each digit for altering the said last transmitted impulse only in case said circuit controlling contacts are operated by said rocker arm in its first position.

12. In an impulse transmitter, a first and a second group of push keys corresponding to different digits, means responsive to the actuation and release of any one of said keys for transmitting a digit comprising a train of impulses corresponding to the actuated key, and means for changing the character of only the last impulse of a transmitted digit only in case the keys of said second group are actuated.

13. In an impulse transmitter, a plurality of push keys corresponding to the different digits, means responsive to the actuation and release of said keys corresponding to the even digits for transmitting digits in code, each of said coded digits comprising one or a train of similar character impulses corresponding in number to onehalf of the value of the digit key actuated, and means including said first means responsive to the actuation and release or" said keys corresponding to odd digits for transmitting digits in code, each of said last mentioned coded digits, except the digit one, comprising one or a train of said similar character impulses corresponding in number to one-half the value of the actuated key followed by the transmission of a last impulse of dissimilar character, and in the case of the code digit transmitted for the digit one comprising only a single impulse of said dissimilar character.

14. In an impulse transmitter, a plurality of digit keys corresponding to digits 1 to 0, inclusive, arranged in three rows, a stationary shaft arranged in parallel relationship with said rows, a lever for each key rotatably mounted on said shaft, and a circular face plate having slots through which the free ends of said levers extend for guiding said levers during operation of said keys thereby confining said keys, shaft and levers within a restricted circular space conforming to said circular face plate for mounting on a telephone set.

15. In an impulse transmitter, ten digit keys corresponding to the digits 1 to 0, inclusive, divided into five pairs of two digit keys each, means responsive to the manual operation of said keys for transmitting one or a train of impulses, the actuation of each key of one of said pairs causing said means to transmit the same number of impulses in the train and the actuation of the keys in the difierent pairs causing said means to transmit diiierent numbers of impulses in the train, and means whereby the last impulse transmitted is of a different character in case the first key of each said pair is actuated.

, 16. In an impulse transmitter, impulsing contact springs normally arranged to transmit pulses of one character, means including said impulsing contact springs for transmitting different series of pulses of said one character corresponding to diiTerent digits, a pair of auxiliary contact springs operated only during the last pulse of each of said series, a pair of grounding contact springs, means for operating said grounding contact springs each time the impulse series corresponds to any one of a plurality of odd digits, and means including said pair of grounding contact springs and said auxiliary contact springs for altering the last pulse of a series from a pulse of said one character to a pulse of a diiierent character dependent upon the operated condition of said pair of grounding contact springs.

17. In an impulse transmitter, a plurality of push buttons corresponding .to difierent digits, impulsing contact springs normally arranged to transmit pulses of one character, means including said impulsing contact springs for transmitting diflerent series of pulses of said one character corresponding to different digits in response to the actuation of said push-buttons, auxiliary contact springs operated only during the last pulse of each of said series, grounding contact springs, means for operating said grounding contact springs dependent upon the value of the actuated push-botton, and means including said pair of grounding contact springs and said auxiliary contact springs for altering the last pulse of a series from a pulse of said one character to a pulse of a difierent character dependent upon the operated condition of said grounding contact springs.

18. In an impulse transmitter, a plurality of push-buttons corresponding to different digits, a pair of impulsing contact springs, means responsive to the actuation and release of any one of said push buttons for separating said pair oi impulsing contact springs a number of times dependent upon the actuated push button, and means also operated responsive to the actuation and release of the actuated push button for grounding one of said impulsing contact springs when it is separated from the other impulsing contact spring by said first means.

19. In an impulse transmitter, a plurality of push buttons corresponding to a plurality of different even digits and to a plurality of odd digits, a pair of impulsing contact springs, means responsive to the actuation and release of any one of said push buttons for separating said impulsing contact springs a number of times corresponding to the actuated push button, and means also operated in response to the actuation and release of only said odd ones of said plurality of push buttons for grounding one of said pair of impulsing contact springs during its last separation from the other impulsing contact spring by said first means.

20. In an impulse transmitter, a plurality of push buttons corresponding to difierent digits, impulse sending means, two circuits over which said impulse sending means normally effects transmission of impulses, means responsive to the actuation and release of any on of said push buttons for operating said impulse sending means to simultaneously transmit impulses over both said two circuits, and means also operated in response to the actuation and release of only certain ones of said plurality of push-buttons for rendering ineffective only one of said two circuits at a predetermined time during said impulse transmission to ther by transmit only one impulse over the other of said two circuits instead of simultaneously over both said circuits.

21. In an impulse transmitter, a plurality of push-buttons corresponding to diiierent di its, impulse sending means, two circuits over which said impulse sending means normally effects transmission of impulses, means responsive to the actuation and release of any one of said push buttons for operating said impulse sending means to transmit a series of impulses corresponding to the actuated push button over said two circuits, each impulse of said series comprising a simultaneous pulse over both said circuits, and means also operated in response to the actuation and release of only predetermined ones of said plurality of push buttons for rendering eiiective only one of said two circuits during only the last impulse of a transmitted series to thereby transmit only one pulse over said one of said two circuits instead of simultaneously over both said circuits for the last impulse of a transmitted series,

22. In a push button calling device, a plurality of push keys corresponding to digits, an impulse wheel, means for rotating said impulse Wheel in response to the actuation and release of an one of said keys, normally closed impulse contact springs separated by the rotation of said impulse wheel a number of times dependent upon the Value of the particular key which is actuated and released, other impulse contacts normally open, means for closing said other impulse contacts once during the rotation of said impulse wheel, the closing taking place concurrently with a particular opening of said first mentioned impulse contact springs, and another set of contacts controlled in accordance with the value of the actuated key for rendering said other Lnpulse contacts ineffective during said particular opening.

23. In a push button callin device, a plurality of push keys corresponding to digits, an impulse wheel, means for rotating said impu se wheel in response to the actuation and release of any one of said keys, normally closed impulse contact springs separated by the rotation of said impulse wheel a number of times dependent upon the value of the particular key which is actuated and released, other impulse contacts normally open, means for closing said other impulse contacts once during the rotation of said impulse wheel,

the closing taking place concurrently with a particular opening of said first mentioned impulse contact springs, and another set of contacts controlled in accordance with the value of the actuated key for altering the character of the impulse corresponding to said particular opening.

ROBERT L. SARGISSON.

AMANDA OBERGFELL, Executrza: of the Estate of Herbert F. Obergfell,

Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Country Date Neuhold Mar. 26, 1912 Clement Aug. 27, 1912 Macadie June 14, 1932 Roberts et a1 Mar. 23, 1943 Richard Jan. 11, 1944 Newel] Sept. 19, 1944 

